This invention relates, in general, to optoelectronic devices and, in particular, to optical interconnect units.
At present, optical fibers are used to transmit optical signals across long distances and typically are not used to transmit light signals short distances or in close association with standard electrical components. However, while waveguides are used to transmit optical signals short distances, waveguides typically are expensive and difficult to make.
Generally, fabrication of optical waveguides is achieved by either a polymer spin-on technique or a diffusion technique, both of which require expensive photolithography steps. Additionally, both fabrication techniques are ineffective and inefficient for fabricating optical waveguides in high volumes for several reasons, such as complex processing steps, difficulties in controlling the processing steps, and high cost.
As practiced by one method in the prior art, a polymeric film is spun onto a substrate. Portions of the polymeric film are subsequently exposed to light by a photolithographic process, thereby changing the refractive index of the polymeric film and creating a waveguide in the polymeric film. However, subsequent multistep processing, such as removal of the polymeric film from the substrate, lamination processing, curing, and other processes typically are required for the waveguide to be useful. Further, it should be noted that each additional processing step incurs an additional cost, as well as presenting an opportunity to induce defects into the waveguide.
Alternatively, in another method practiced in the prior art, a layer such as a glass is applied to a substrate. The layer is patterned by a complicated photolithography process, thereby producing portions that are masked and portions that are open or clear. Typically, ions are subsequently diffused into the open portions of the layer, thus changing the refractive index of the layer and making a waveguide. However, using a photolithography process results in a high cost of manufacturing. Also, by using diffusion processes to change the refractive index of the layer, control of dimensionality of the waveguide is severely limited.
It can be readily seen that conventional methods for making waveguides have serious limitations. Also, it is evident that the conventional processing uses a multitude of steps, which are not only complex and expensive, but also not effective processing. Therefore, a method for making an optical interconnect unit that provides a reduction in the number of steps, simplifies the process, reduces cost, would be highly desirable.